Constitutive high-level expression of a codon-optimized β-fructosidase gene from the hyperthermophile Thermotoga maritima in Pichia pastoris

Industrial Approach to Invertase Production from Fruit Waste for Enhanced Efficiency and Conservation

This study investigates the commercial viability of repurposing fruit waste for enzyme production, specifically focusing on the invertase enzyme derived from Saccharomyces cerevisiae. By utilizing fruit pulp that incorporates mulberry, carob, Figure, and grape pulp as a nutrient source, it is observed that the culture medium containing carob pulp exhibits the highest invertase activity. Specifically, the invertase activity in this medium is approximately 2.5 times greater (12.90 U/mg protein) than that observed in the peptone medium (5.98 U/mg protein). The extract undergoes several purification steps, including ultrafiltration, ammonium sulfate precipitation, dialysis, and ion-exchange chromatography (purification ratio: 12.11 times, yield: 26.93%). The purified enzyme is immobilized using alginate beads, improving pH and thermal stability. The immobilized enzyme exhibits optimal activity between pH 3.50 and pH 7.00, thereby broadening the enzyme's high-activity pH range. The thermal stability of the immobilized invertase enzyme is significantly improved, especially at 65 °C. Activity studies in the presence of metal ions and certain chemicals have been conducted. The immobilized enzyme's activity increases by approximately 40% in the presence of Ca2+ and Mg2+, and the immobilized enzyme maintains its activity in the presence of detergents such as SDS, Tween-20, and organic solvents like ethanol and methanol. The potential for the reuse of immobilized invertase was investigated under standard assay conditions. After 20 cycles, the immobilized enzyme was found to retain 80% of its initial activity. Overall, the study establishes the commercial potential of fruit pulp, typically discarded in fruit juice production, as a valuable source for obtaining an invertase enzyme. Furthermore, this study also aims to develop a suitable purification process for invertase in the fruit juice industry. By harnessing fruit waste and implementing innovative enzyme production strategies, industries can enhance their efficiency, reduce their environmental footprint, and optimize resource utilization.

Evaluation of different glycerol fed-batch strategies in a lab-scale bioreactor for the improved production of a novel engineered β-fructofuranosidase enzyme in Pichia pastoris

The β-fructofuranosidase enzyme from Aspergillus niger has been extensively used to commercially produce fructooligosaccharides from sucrose. In this study, the native and an engineered version of the β-fructofuranosidase enzyme were expressed in Pichia pastoris under control of the glyceraldehyde-3-phosphate dehydrogenase promoter, and production was evaluated in bioreactors using either dissolved oxygen (DO-stat) or constant feed fed-batch feeding strategies. The DO-stat cultivations produced lower biomass concentrations but this resulted in higher volumetric activity for both strains. The native enzyme produced the highest volumetric enzyme activity for both feeding strategies (20.8% and 13.5% higher than that achieved by the engineered enzyme, for DO-stat and constant feed, respectively). However, the constant feed cultivations produced higher biomass concentrations and higher volumetric productivity for both the native as well as engineered enzymes due to shorter process time requirements (59 h for constant feed and 155 h for DO-stat feed). Despite the DO-stat feeding strategy achieving a higher maximum enzyme activity, the constant feed strategy would be preferred for production of the β-fructofuranosidase enzyme using glycerol due to the many industrial advantages related to its enhanced volumetric enzyme productivity.

Recombinant protein production in Pichia pastoris: From transcriptionally redesigned strains to bioprocess optimization and metabolic modelling

Pichia pastoris is one of the most widely used host for the production of recombinant proteins. Expression systems that rely mostly on promoters from genes encoding alcohol oxidase 1 or glyceraldehyde-3-phosphate dehydrogenase have been developed together with related bioreactor operation strategies based on carbon sources such as methanol, glycerol, or glucose. Although, these processes are relatively efficient and easy to use, there have been notable improvements over the last twenty years to better control gene expression from these promoters and their engineered variants. Methanol-free and more efficient protein production platforms have been developed by engineering promoters and transcription factors. The production window of P. pastoris has been also extended by using alternative feedstocks including ethanol, lactic acid, mannitol, sorbitol, sucrose, xylose, gluconate, formate, or rhamnose. Herein, the specific aspects that are emerging as key parameters for recombinant protein synthesis are discussed. For this purpose, a holistic approach has been considered to scrutinize protein production processes from strain design to bioprocess optimization, particularly focusing on promoter engineering, transcriptional circuitry redesign. This review also considers the optimization of bioprocess based on alternative carbon sources and derived co-feeding strategies. Optimization strategies for recombinant protein synthesis through metabolic modelling are also discussed.

Enhanced Secretory Expression and Surface Display Level of Bombyx mori Acetylcholinesterase 2 by Pichia pastoris Based on Codon Optimization Strategy for Pesticides Setection

The cholinesterase-based spectrophotometric assay, also called enzyme inhibition method, is a good choice for rapid detection of organophosphate pesticides (OPs) and carbamate pesticides (CPs). Obviously, the cholinesterase is the core reagent in enzyme inhibition method. In our previous work, a recombinant acetylcholinesterase 2 from Bombyx mori (rBmAChE2) was expressed in yeast successfully and exhibited great sensitivity. However, the yield of rBmAChE2 is not desirable. In this study, a codon optimization strategy was employed to enhance the yield of rBmAChE2 in Pichia pastoris GS115. Results showed that by replacing 6 key rare codons and increasing the percentage of bases G and C up to 46.85%, codon adaptation index (CAI) of Bombyx mori acetylcholinesterase 2 (bmace2) gene was improved from 0.70 to 0.81. After being transformed into Pichia pastoris GS115 via electroporation, the expression transformant can produce 139.7 U/mL secretory codon-optimized rBmAChE2 (opt-rBmAChE2) in the culture supernatant, 3.62 times higher than that of strain bearing the wild-type bmace2 gene. Meanwhile, opt-rBmAChE2 displayed on the yeast surface was up to 2280.02 U/g, 2.8 times higher than wild-type displayed rBmAChE2. In addition, either secretory or surface-displayed opt-rBmAChE2 maintained the similar sensitivities to the wild-type rBmAChE2 for tested inhibitors. Furthermore, the detection limits of the opt-rBmAChE2-based enzyme inhibition method for 10 kinds of OPs or CPs (0.01-2.69 mg/kg) were lower than most of the indexes present in current standard method (GB/T 5009.199-2003) or the maximum residue limits (GB 2763-2019) in China. The results might contribute to the utilization of rBmAChE2 for pesticide residue screening detection in practice.

Identification of an Invertase With High Specific Activity for Raffinose Hydrolysis and Its Application in Soymilk Treatment

The hydrolyzation of raffinose into melibiose by using invertases under mild conditions improves the nutritional value of soybean products. However, this strategy has received little attention because a suitable invertase remains lacking. In this study, a novel invertase named InvDz13 was screened and purified from Microbacterium trichothecenolyticum and characterized. InvDz13 was one of the invertases with the highest specific activity toward raffinose. Specifically, it had a specific activity of 229 U/mg toward raffinose at pH 6.5 and 35°C. InvDz13 retained more than 80% of its maximum activity at pH 5.5–7.5 and 25–40°C and was resistant to or stimulated by most cations that presented in soymilk. In soymilk treated with InvDz13 under mild conditions, melibiose concentration increased from 3.1 ± 0.2 to 6.1 ± 0.1 mM due to raffinose hydrolyzation by InvDz13. Furthermore, the prebiotic property of InvDz13-treated soymilk was investigated via in vitro fermentation by human gut microbiota. Results showed that InvDz13 treatment increased the proportion of the beneficial bacteria Bifidobacterium and Lactobacillus by 1.6- and 3.7-fold, respectively. By contrast, the populations of Escherichia and Collinsella decreased by 1.8- and 11.7-fold, respectively. Thus, our results proved that the enzymatic hydrolysis of raffinose in soymilk with InvDz13 was practicable and might be an alternative approach to improving the nutritional value of soymilk.

Removal of bacterial dextran in sugarcane juice by Talaromyces minioluteus dextranase expressed constitutively in Pichia pastoris

A gene construct encoding the mature region of Talaromyces minioluteus dextranase (EC 3.2.1.11) fused to the Saccharomyces cerevisiae SUC2 signal sequence was expressed in Pichia pastoris under the constitutive glyceraldehyde 3-phosphate dehydrogenase promoter (pGAP). The increase of the transgene dosage from one to two and four copies enhanced proportionally the extracellular yield of the recombinant enzyme (r-TmDEX) without inhibiting cell growth. The volumetric productivity of the four-copy clone in fed batch fermentation (51 h) using molasses as carbon source was 1706 U/L/h. The secreted N-glycosylated r-TmDEX was optimally active at pH 4.5-5.5 and temperature 50-60 °C. The addition of sucrose (600 g/L) as a stabilizer retained intact the r-TmDEX activity after 1-h incubation at 50-60 °C and pH 5.5. Bacterial dextran in deteriorated sugarcane juice was completely removed by applying a crude preparation of secreted r-TmDEX. The high yield of r-TmDEX in methanol-free cultures and the low cost of the fed batch fermentation make the P. pastoris pGAP-based expression system appropriate for the large scale production of dextranase and its use for dextran removal at sugar mills.

Fed-Batch Production of Saccharomyces cerevisiae L-Asparaginase II by Recombinant Pichia pastoris MUT s Strain

L-Asparaginase (ASNase) is used in the treatment of acute lymphoblastic leukemia, being produced and commercialized only from bacterial sources. Alternative Saccharomyces cerevisiae ASNase II coded by the ASP3 gene was biosynthesized by recombinant Pichia pastoris MUT s under the control of the AOX1 promoter, using different cultivation strategies. In particular, we applied multistage fed-batch cultivation divided in four distinct phases to produce ASNase II and determine the fermentation parameters, namely specific growth rate, biomass yield, and enzyme activity. Cultivation of recombinant P. pastoris under favorable conditions in a modified defined medium ensured a dry biomass concentration of 31 gdcw.L-1 during glycerol batch phase, corresponding to a biomass yield of 0.77 gdcw.gglycerol - 1 and a specific growth rate of 0.21 h-1. After 12 h of glycerol feeding under limiting conditions, cell concentration achieved 65 gdcw.L-1 while ethanol concentration was very low. During the phase of methanol induction, biomass concentration achieved 91 gdcw.L-1, periplasmic specific enzyme activity 37.1 U.gdcw - 1 , volumetric enzyme activity 3,315 U.L-1, overall enzyme volumetric productivity 31 U.L-1.h-1, while the specific growth rate fell to 0.039 h-1. Our results showed that the best strategy employed for the ASNase II production was using glycerol fed-batch phase with pseudo exponential feeding plus induction with continuous methanol feeding.

Efficient heterologous expression of an alkaline lipase and its application in hydrolytic production of free astaxanthin

BACKGROUND

Astaxanthin, a naturally occurring carotenoid pigment molecule, displays strong antioxidant, anti-cancer, and immunity-enhancing properties, and is often utilized in food, biomedical, cosmetic, and other industries. Free astaxanthin has better solubility than astaxanthin esters (Ast-E), and is a useful auxiliary ingredient in health foods and medicines. Our goal was to establish an improved enzymatic method for preparation of free astaxanthin from natural sources (e.g., the microalga Haematococcus pluvialis), to expand the potential applications of free astaxanthin.

RESULTS

The alkaline lipase gene proalip and its propeptide were cloned and successfully fusion-expressed in Pichia pastoris X-33. The recombinant lipase was termed Lipase-YH. Through optimization of culture conditions (medium formulation, pH, added methanol concentration), cell growth (OD₆₀₀) and secreted enzyme activity respectively reached to 280 and 2050 U/mL in a 50-L autofermentor. Activity of Lipase-YH enzyme powder was about 40,000 U/g. Hydrolysis of Ast-E (extracted from H. pluvialis) by Lipase-YH occurred in aqueous phase, and reaction conditions were optimized based on emulsification method and enzyme/substrate ratio. The highest enzymatic reaction rate was observed for substrate concentration 200 μg/mL, with maximal free astaxanthin yield (80%) at 1 h, and maximal Ast-E hydrolysis rate 96%, as confirmed by TLC, HPLC, and mass spectroscopy.

CONCLUSION

A novel, efficient enzymatic process was developed for production of free astaxanthin through hydrolysis of Ast-E. Lipase activity was enhanced, and production cost was greatly reduced. The unique structure of free astaxanthin allows linkage to various functional compounds, which will facilitate development of novel pharmaceutical and food products in future studies.

A panorama of bacterial inulinases: Production, purification, characterization and industrial applications

Inulinases are important hydrolysing enzymes which specifically act on β-2, 1 linkages of inulin to produce fructose or fructooligosaccharides. Fungi, yeasts and bacteria are the potent microbial sources of inulinases. The data on bacterial inulinases is scarce as compared to other microbial sources. Inulinases yield from bacteria is very less as compared to fungal and yeast sources of inulinases. Submerged fermentation (SmF) is the method of choice for the production of inulinases from bacterial sources. Moreover, inulin is a potent substrate for the production of inulinases in SmF. Many bacterial inulinases have been reported to display magnificent environment abiding features and variability in their biophysical and biochemical properties. These properties have attracted intention of many researchers towards exploring adverse ecological niches for more distinctive inulinase producing bacterial strains. Inulinases are substantially important in current biotechnological era due to their numerous industrial applications. High fructose syrup and fructooligosaccharides are two major industrial applications of inulinases. Additionally, there are many reports on the production of various metabolites like citric acid, lactic acid, ethanol, biofuels, butanediol etc. using mixed cultures of inulinase producing organisms with other microorganisms. The present review mainly envisages inulinase producing bacterial sources, inulinase production, purification, characterization and their applications.

Extracellular expression and antiviral activity of a bovine interferon-alpha through codon optimization in Pichia pastoris

Interferons (IFNs) are the primary line of defense against infectious agents. In particular, IFN-α is an important antiviral cytokine and has a wide range of immune-modulating functions. Porcine and human IFN-α have been successfully prepared and play important roles in the prevention and therapy of viral diseases. To date, there has been limited applied research on bovine IFN-α. To achieve high-level expression of recombinant bovine IFN-α (bIFN-α) in Pichia pastoris for large-scale application, the bIFN-α gene was optimized and synthesized on the basis of codon bias of P. pastoris. Optimized bIFN-α (opti-bIFN-α) was successfully expressed in P. pastoris and directly secreted into the culture supernatant. The amount of extracellular soluble opti-bIFN-α was observed to be 200μg/mL in a shake flask. Expression efficiency of opti-bIFN-α was found to be about three times that of wild-type bIFN-α when the expression yield was compared at the same copies of the targeted gene. In addition, both the original cultural supernatant and purified opti-bIFN-α showed strong antiviral activity in MDBK cells (2×10(6)AU/mL and 1×10(7)AU/mg, respectively) and IBRS-2 cells (3×10(5)AU/mL and 1.5×10(6)AU/mg, respectively) against a recombinant vesicular stomatitis virus expressing the green fluorescence protein. In this study, we demonstrated high-level extracellular expression of opti-bIFN-α by P. pastoris. To the best of our knowledge, the opti-bIFN-α yield observed in this study is the highest to be reported to date. Our results demonstrated that the extracellular opti-bIFN-α with strong antiviral activity could be easily prepared and purified at a low cost and that it may be a potential biological therapeutic drug against bovine viral infections.

Highly Efficient Fructooligosaccharides Production by an Erythritol-Producing Yeast Yarrowia lipolytica Displaying Fructosyltransferase

Currently, fructooligosaccharides (FOS) are industrially transformed from sucrose by purified enzymes or fungi cells. However, these methods are expensive and time-consuming. An economical approach to producing FOS using erythritol-producing yeast cells was described in this study. Fructosyltransferase from Aspergillus oryzae was displayed on the cell surface of Yarrowia lipolytica, resulting in an engineered strain capable of transforming sucrose to FOS. An amount of 480 g/L FOS was produced within 3 h in a solution of 800 g/L sucrose and 5 g/L cells (dry cell weight, DCW) at pH 6.0 and 60 °C, with a yield of 60% of total sucrose and a productivity of 160 g/(L·h). The yeast pastes from the erythritol industry can be repeatedly used as the whole-cell catalysts at least 10 times by this newly developed approach. This efficient method is attractive for the large-scale production of FOS from sucrose.

A comparative molecular dynamics study of thermophilic and mesophilic β-fructosidase enzymes

Arabidopsis thaliana cell wall invertase 1 (AtcwINV1) and Thermotoga maritima β-fructosidase (BfrA) are among the best structurally studied members of the glycoside hydrolase family 32. Both enzymes hydrolyze sucrose as the main substrate but differ strongly in their thermal stability. Mesophilic AtcwINV1 and thermophilic BfrA have divergent sequence similarities in the N-terminal five bladed β-propeller catalytic domain (31 %) and the C-terminal β-sandwich domain (15 %) of unknown function. The two enzymes were subjected to 200 ns molecular dynamics simulations at 300 K (27 °C) and 353 K (80 °C). Regular secondary structure regions, but not loops, in AtcwINV1 and BfrA showed no significant fluctuation differences at both temperatures. BfrA was more rigid than AtcwINV1 at 300 K. The simulation at 353 K did not alter the structural stability of BfrA, but did increase the overall flexibility of AtcwINV1 exhibiting the most fluctuating regions in the β-propeller domain. The simulated heat treatment also increased the gyration radius and hydrophobic solvent accessible surface area of the plant enzyme, consistent with the initial steps of an unfolding process. The preservation of the conformational rigidity of BfrA at 353 K is linked to the shorter size of the protein loops. Shortening of BfrA loops appears to be a key mechanism for thermostability.

Purification, cloning, characterization, and N-glycosylation analysis of a novel β-fructosidase from Aspergillus oryzae FS4 synthesizing levan- and neolevan-type fructooligosaccharides

β-Fructosidases are a widespread group of enzymes that catalyze the hydrolysis of terminal fructosyl units from various substrates. These enzymes also exhibit transglycosylation activity when they function with high concentrations of sucrose, which is used to synthesize fructooligosaccharides (FOS) in the food industry. A β-fructosidase (BfrA) with high transglycosylation activity was purified from Aspergillus oryzae FS4 as a monomeric glycoprotein. Compared with the most extensively studied Aspergillus spp. fructosidases that synthesize inulin-type β-(2-1)-linked FOS, BfrA has unique transfructosylating property of synthesizing levan- and neolevan-type β-(2-6)-linked FOS. The coding sequence (bfrAFS4, 1.86 kb) of BfrA was amplified and expressed in Escherichia coli and Pichia pastoris. Both native and recombinant proteins showed transfructosylation and hydrolyzation activities with broad substrate specificity. These proteins could hydrolyze the following linkages: Glc α-1, 2-β Fru; Glc α-1, 3-α Fru; and Glc α-1, 5-β Fru. Compared with the unglycosylated E. coli-expressed BfrA (E.BfrA), the N-glycosylated native (N.BfrA) and the P. pastoris-expressed BfrA (P.BfrA) were highly stable at a wide pH range (pH 4 to 11), and significantly more thermostable at temperatures up to 50°C with a maximum activity at 55°C. Using sucrose as substrate, the Km and kcat values for total activity were 37.19±5.28 mM and 1.0016±0.039×104 s-1 for N.BfrA. Moreover, 10 of 13 putative N-glycosylation sites were glycosylated on N.BfrA, and N-glycosylation was essential for enzyme thermal stability and optima activity. Thus, BfrA has demonstrated as a well-characterized A. oryzae fructosidase with unique transfructosylating capability of synthesizing levan- and neolevan-type FOS.

Complete sucrose hydrolysis by heat-killed recombinant Pichia pastoris cells entrapped in calcium alginate

Background

An ideal immobilized biocatalyst for the industrial-scale production of invert sugar should stably operate at elevated temperatures (60-70°C) and high sucrose concentrations (above 60%, w/v). Commercial invertase from the yeast Saccharomyces cerevisiae is thermolabile and suffers from substrate inhibition. Thermotoga maritima β-fructosidase (BfrA) is the most thermoactive and thermostable sucrose-hydrolysing enzyme so far identified and allows complete inversion of the substrate in highly concentrated solutions.

Results

In this study, heat-killed Pichia pastoris cells bearing N-glycosylated BfrA in the periplasmic space were entrapped in calcium alginate beads. The immobilized recombinant yeast showed maximal sucrose hydrolysis at pH 5–7 and 90°C. BfrA was 65% active at 60°C and had no activity loss after incubation without the substrate at this temperature for 15 h. Complete inversion of cane sugar (2.04 M) at 60°C was achieved in batchwise and continuous operation with respective productivities of 4.37 and 0.88 gram of substrate hydrolysed per gram of dry beads per hour. The half-life values of the biocatalyst were 14 and 20 days when operated at 60°C in the stirred tank and the fixed-bed column, respectively. The reaction with non-viable cells prevented the occurrence of sucrose fermentation and the formation of by-products. Six-month storage of the biocatalyst in 1.46 M sucrose (pH 5.5) at 4°C caused no reduction of the invertase activity.

Conclusions

The features of the novel thermostable biocatalyst developed in this study are more attractive than those of immobilized S. cerevisiae cells for application in the enzymatic manufacture of inverted sugar syrup in batch and fixed-bed reactors.

Improved production of a recombinant Rhizomucor miehei lipase expressed in Pichia pastoris and its application for conversion of microalgae oil to biodiesel

BACKGROUND

We previously cloned a 1,3-specific lipase gene from the fungus Rhizomucor miehei and expressed it in methylotrophic yeast Pichia pastoris strain GS115. The enzyme produced (termed RML) was able to catalyze methanolysis of soybean oil and showed strong position specificity. However, the enzyme activity and amount of enzyme produced were not adequate for industrial application. Our goal in the present study was to improve the enzyme properties of RML in order to apply it for the conversion of microalgae oil to biofuel.

RESULTS

Several new expression plasmids were constructed by adding the propeptide of the target gene, optimizing the signal peptide, and varying the number of target gene copies. Each plasmid was transformed separately into P. pastoris strain X-33. Screening by flask culture showed maximal (21.4-fold increased) enzyme activity for the recombinant strain with two copies of the target gene; the enzyme was termed Lipase GH2. The expressed protein with the propeptide (pRML) was a stable glycosylated protein, because of glycosylation sites in the propeptide. Quantitative real-time RT-PCR analysis revealed two major reasons for the increase in enzyme activity: (1) the modified recombinant expression system gave an increased transcription level of the target gene (rml), and (2) the enzyme was suitable for expression in host cells without causing endoplasmic reticulum (ER) stress. The modified enzyme had improved thermostability and methanol or ethanol tolerance, and was applicable directly as free lipase (fermentation supernatant) in the catalytic esterification and transesterification reaction. After reaction for 24 hours at 30°C, the conversion rate of microalgae oil to biofuel was above 90%.

CONCLUSIONS

Our experimental results show that signal peptide optimization in the expression plasmid, addition of the gene propeptide, and proper gene dosage significantly increased RML expression level and enhanced the enzymatic properties. The target enzyme was the major component of fermentation supernatant and was stable for over six months at 4°C. The modified free lipase is potentially applicable for industrial-scale conversion of microalgae oil to biodiesel.

Identification of the gene for β-fructofuranosidase from Ceratocystis moniliformis CMW 10134 and characterization of the enzyme expressed in Saccharomyces cerevisiae

Background

β-Fructofuranosidases (or invertases) catalyse the commercially-important biotransformation of sucrose into short-chain fructooligosaccharides with wide-scale application as a prebiotic in the functional foods and pharmaceutical industries.

Results

We identified a β-fructofuranosidase gene (CmINV) from a Ceratocystis moniliformis genome sequence using protein homology and phylogenetic analysis. The predicted 615 amino acid protein, CmINV, grouped with an existing clade within the glycoside hydrolase (GH) family 32 and showed typical conserved motifs of this enzyme family. Heterologous expression of the CmINV gene in Saccharomyces cerevisiae BY4742∆suc2 provided further evidence that CmINV indeed functions as a β-fructofuranosidase. Firstly, expression of the CmINV gene complemented the inability of the ∆suc2 deletion mutant strain of S. cerevisiae to grow on sucrose as sole carbohydrate source. Secondly, the recombinant protein was capable of producing short-chain fructooligosaccharides (scFOS) when incubated in the presence of 10% sucrose. Purified deglycosylated CmINV protein showed a molecular weight of ca. 66 kDa and a K_m and V_max on sucrose of 7.50 mM and 986 μmol/min/mg protein, respectively. Its optimal pH and temperature conditions were determined to be 6.0 and 62.5°C, respectively. The addition of 50 mM LiCl led to a 186% increase in CmINV activity. Another striking feature was the relatively high volumetric production of this protein in S. cerevisiae as one mL of supernatant was calculated to contain 197 ± 6 International Units of enzyme.

Conclusion

The properties of the CmINV enzyme make it an attractive alternative to other invertases being used in industry.

Codon modification for the DNA sequence of a single-chain Fv antibody against clenbuterol and expression in Pichia pastoris

The expression efficiency was improved for the recombinant single-chain variable fragment (scFv) against clenbuterol (CBL) obtained from mouse and expressed in the methylotrophic yeast Pichia pastoris GS115, by redesigning and synthesizing the DNA sequence encoding for CBL-scFv based on the codon bias of P. pastoris. The codons encoding 124 amino acids were optimized, in which a total of 156 nucleotides were changed, and the G+C ratio was simultaneously decreased from 53 to 47.2 %. Under the optimized expression conditions, the yield of the recombinant CBL-scFv (41 kDa) antibodies was 0.223 g L⁻¹ in shake culture. Compared to the non-optimized control, the expression level of the optimized recombinant CBL-scFv based on preferred codons in P. pastoris demonstrated a 2.35-fold higher yield. Furthermore, the recombinant CBL-scFv was purified by Ni-NTA column chromatography, and the purity was 95 %. The purified CBL-scFv showed good CBL recognition by a competitive indirect enzyme-linked immunoassay. The average concentration required for 50 % inhibition of binding and the limit of detection for the assay were 5.82 and 0.77 ng mL⁻¹, respectively.

Expression, purification, and immunogenic characterization of Epstein-Barr virus recombinant EBNA1 protein in Pichia pastoris

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumors. EBNA1 is the only viral protein expressed in all EBV-associated malignancies and plays important roles in EBV latency. Thus, EBNA1 is thought to be a promising antigen for immunotherapy of all EBV-associated malignancies. This study was undertaken to produce recombinant EBNA1 protein in Pichia pastoris and evaluate its immunogenicity. The truncated EBNA1 (E1ΔGA, codons 390-641) was expressed as a secretory protein with an N-terminal histidine tag in the methylotrophic yeast P. pastoris and purified by Ni-NTA affinity chromatography. The purified proteins were then used as antigens to immunize BALB/c mice for production of polyclonal antibodies. Western blot analysis showed that the polyclonal antibodies specifically recognized the EBNA1 protein in B95-8 cell lysates. The recombinant E1ΔGA also induced strong lymphoproliferative and Th1 cytokine responses in mice. Furthermore, mice immunized with E1ΔGA developed CD4+ and CD8+ T cell responses. These findings showed that the yeast-expressed E1ΔGA retained good immunogenicity and might be a promising vaccine candidate against EBV-associated malignancies.